1. Field of the Invention
The invention relates to the field of adapter cards, and in particular, to use of vendor unique connections in a standard adapter card bus specification.
2. Background Information
In many computer systems, input/output (I/O) interfacing and other special purpose circuitry is often provided using add-on adapter cards which conveniently and simply plug-in to standard bus connectors on a processor mother-board or backplane. A variety of adapter/connector/bus types and standards are known, and one of these is the peripheral component interconnect (PCI) standard.
Standardization provides inherent advantages both for consumers and manufacturers, but also has inherent limitations. A clear advantage of PCI standardization is predictable interchangeability, which gives consumers a wide selection of adapter cards and manufacturers to choose from, and gives manufacturers a large pool of consumers to target. However, as can be readily appreciated, PCI standardization may have the effect of limiting PCI adapter card functionality because of the constraints imposed on the type and number of signals available through the PCI connector. Vendors/manufacturers of PCI adapter cards, motherboards/backplanes and systems (boxes), have an inherent need to differentiate their PCI platforms from the crowd of competitors to gain a marketing advantage over their competitors by providing enhanced functionality. Therefore, a clear disadvantage of PCI standardization is the constraint it places on the ability to customize circuitry to provide enhanced functionality.
In particular, since the current PCI standard does not allow for "vendor unique" connections from PCI adapter cards to PCI motherboards/backplanes through the PCI standard edge connector, customization is limited to what can be accommodated by the standard edge connector. However, the PCI bus standard currently has a number of reserved (RSVD) pins on the edge connector, reserved for future definition and standardization. Presently, there are nine PCI RSVD pins: A09, A11, B10, B14, B63, B92, B93, A92 and A94. There are also some pins which may be infrequently used, such as A14 and A19, for example.
A number of PCI card and backplane vendors, including International Business Machines Corporation, have already made use of some of the reserved pins on the PCI bus connector for proprietary purposes to overcome the customization limitation.
However, as the PCI community continues to define standard uses of these RSVD pins, these legacy cards and backplanes, that is, cards and backplanes on which some RSVD pins are used for proprietary purposes, may experience compatibility problems with systems designed according to a redefined PCI standard. Such problems, of course, negate any marketing advantages that these legacy devices had when they were compatible with the PCI standard.
Currently, the problem of a lack of vendor unique connections in the PCI standard is being addressed by a PCI industrial standards group called PCI Industrial Computer Manufacturers Group (PICMG) which is advancing a new standard called CompactPCI. This new standard is an adaptation of the desktop PCI specification. Among other things, CompactPCI allows a large number of vendor unique connections to a backplane.
However, the CompactPCI solution to the problem of providing vendor unique connections has some drawbacks and limitations. In particular, because CompactPCI is not an ANSI (American National Standards Institute) approved PCI standard, and mainly targets a particular segment of the total PCI market, the advantage of volume acceptance of this solution is currently limited. Further, CompactPCI uses a completely different connector configuration from the current PCI standard connector which raises forward and backward compatibility issues (for the CompactPCI specification, see the PCI Industrial Computer Manufacturers Group website at www.picmg.orglacompactpci.htm).
Therefore, a need exists for a way to accommodate vendor unique differentiation/customization while maintaining the required degree of compatibility and standardization.